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In this chapter, we are going to look at an important After Effects feature called Pre-composing. Basically, that is when you take a series of layers and group them together into another composition. There is a few reasons why you'd want to do that, and I have a few examples for you. So, hopefully that idea will crystallize as we go through these. Basically, I want to reiterate the problem we have with our last example. We had this biker girl who is biking and she's actually made up of several layers. There is pedals and a crank and the bike and she has two Legs, and there's a lot there.
So, animating her like kind of driving on the screen is a little bit more complex in that. So, what we are going to do is we are going to group these layers together into a composition that will be a layer in this composition. So, click on layer #6, the Biker Body layer - that's the topmost layer - and then hold the Shift key down and click on layer 12, the Biker Right Leg layer, which is an extreme tongue twister. With all of these layers selected, from layer 6 to layer 12, make sure they are all highlighted here, go to the Layer menu and choose Pre-compose.
You could also use the keyboard shortcut, Command+Shift+C or Ctrl+Shift+C on the PC. If you are new to After Effects, you might not need to worry about that. But if you want to be a pro in After Effects, this is one of those keyboard shortcuts that you almost always will use every time you open the program. So, I am going to select Pre- compose here, and I am going to call this PRECOMP, in capital letters, just so I know, visually, that this is a pre-composed composition. I'll call this bike girl for lack of a more intelligent-sounding comp name.
I'll go ahead and click OK. Now, what that did was it compressed all those layers or grouped all those layers into one composition. So, all those layers are still here and if we were to visually preview this composition, we wouldn't see any difference, visually. Just as far as organization goes, these are all now grouped in one nested composition. The benefit of that is that now as we open up this layer, we have access to all of the Transform properties for this entire group.
So, now we can go out to about here. Actually, let's go ahead and set a keyframe for right about there. Let's click the stopwatch for position because we want her to end up at about two seconds and six frames in. We want her to end up at this frame, at this spot, then move a little earlier, say about here. We'll drag the X axis - that's the left property of the position - to the right, and that will drive her offscreen there, exit stage right to you, bike girl.
Then as we preview this, the bike girl comes on in and actually, she starts animating a little bit earlier. So, what I can do is just click on this layer and drag it to the left, so her animation starts a little bit earlier. We just need to click and drag around our keyframes, drag them to the right a little bit and she comes in pedaling, like a champ.
But the real point here is that we can now operate all of these layers as if they were one whole, so we could scale them all together, and we can rotate them all together. We could fade them out or fade them in all together. So, it really is a great way, not only just to keep yourself organized, but to be able to affect multiple properties as one whole. Here is another example of how that's often used. I have this knight here, some great art from a buddy of mine named Will Kendrick.
He has this knife and he kind of stabs there, very cool. You could see all of the layers. This is a very complex character, and there are different layers for every single piece and component of this knight. So, as we scrub in time here, he stabs, and that's really cool. But what if we want to move this knight around or treat him as one and complete whole? Well, that's when we would pre-compose. So, here is the difference between not precomposed, and then here is the PRECOMPOSED (PRECOMP knight) layer, just one layer in a composition.
So, we could go over to like this castle scene here. I could go into my Project panel, find the PRECOMPOSED layer, which is the PRECOMPOSED knight, and drag this in, just as if it were some video element, although it's not a video; it's just a composition. But After Effects will treat it like a video. So, again, hit S for Scale and scale this guy down, really small, maybe about 10%, somewhere around there. Click and drag and move him wherever you'd like to put him in the scene and maybe even like 8% ,because 10% is too big.
You could see that he is stabbing there. He still has the same animation. What we could do is select this layer and hit Command+D on the Mac or Ctrl+D on the PC, which will duplicate that layer. We could click and drag and keep doing that. Ctrl+D to duplicate, Command+D on the Mac to duplicate. Oops! The duplicate's over here. If we wanted to, let me make one more duplicate here. I'll Command+D or Ctrl+D put this guy over here.
Open up S for Scale and if we unlink Scale, and then we take like, let's say, for example, the X axis to a negative value, it will actually flip the layer. So, if I type in -8, it flips this guy. So, now he is a bad guy or maybe he is defending the castle, and these guys are bad guys or something. He is on the opposing team. Also, you could see if we scale this, like one of the properties, too much, this is what happens. It kind of flips over on itself, which is a little bit weird, but it does allow you to completely flip a layer.
Now, I could then add a Color Affect, I could play with these in time, and we basically have a battle. Right now, it's kind of like a synchronized medieval knight stabbings. But if we were to offset these in time, play with colors a little bit, then we would have an army made very quickly through Pre-composing. You could imagine taking all of these crazy layers and putting them into this castle scene. It would just be impossible, because there will be too many layers, and we wouldn't be able to control the entire knight at once.
So, Pre-composing does good for organizing your scene, allowing you to apply transforms to a group of layers.
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